JP2013510929A - Smear-resistant inkjet ink - Google Patents

Abstract

The present invention relates to an inkjet ink comprising a polyurethane dispersion and a self-dispersing pigment, particularly a smear-resistant inkjet ink, and more particularly a smear-resistant pigmented aqueous inkjet ink. The polyurethane dispersion has a glass transition temperature Tg of greater than −30 ° C. to less than about 35 ° C. and a loss modulus E ″ and / or peak loss tangent of 1.7 to 5 × 10 ⁸ Pascals of 0.23 to Having at least one of the thermal properties of 0.65, where glass transition temperature, peak loss tangent and loss modulus are measured by dynamic mechanical analysis on films prepared from polyurethane dispersions Is done.

Description

The present invention has a glass transition temperature Tg of more than −30 ° C. to less than 35 ° C., and 1) a loss elastic modulus E ″ of 1.7 to 5 × 10 ⁸ pascals and 2) a peak loss tangent of 0 It relates to an inkjet ink comprising a polyurethane dispersion having at least one of the thermal properties of .23 to 0.65, in particular a smear-resistant inkjet ink and more particularly a smear-resistant pigmented aqueous inkjet ink. The pigment used is a self-dispersing pigment.

  Both dyes and pigments have been used as colorants for inkjet inks. Dyes typically provide superior color properties compared to pigments, but fade quickly and are more susceptible to abrasion. Inks containing pigments dispersed in an aqueous medium are advantageously superior to inks using water-soluble dyes in terms of water fastness and sunlight fastness of the printed image.

  Suitable pigments for aqueous inkjet inks are generally well known in the art. Traditionally, pigments have been stabilized with a dispersant, such as a polymer dispersant or a surfactant, to produce a stable dispersion of the pigment in the vehicle. More recently, however, so-called “self-dispersible” or “self-dispersing” pigments (hereinafter “SDP”) have been developed. As the name implies, SDP can be dispersed in water without a dispersant.

  SDP is often advantageous over conventional dispersant-stabilized pigments in that it provides greater stability and lower viscosity in the same pigment.

  Although advantageous in some respects, permeable pigment-based ink compositions may somewhat reduce the color development when the ink is printed on plain paper. Increasing the pigment content may improve color development, but generally increases the viscosity of the ink and is therefore often detrimental to the ejection stability of the ink. However, because SDP has beneficial properties, it is possible to feed these pigments to higher levels while reducing the impact on viscosity. Thus, penetrating inks with excellent color development are still possible by using SDP.

  Despite these potential benefits brought about by the use of SDP, inks formulated with SDP tend to have some poor fixing on recording media, particularly plain paper. One example of fixing failure is when ink is soiled when a highlighter pen is used on an ink jet printed image.

  Nevertheless, there is a need for inkjet inks that have excellent dispersion stability and ejection stability, including SDP, which can be printed on plain paper with excellent color and is smear resistant.

  One embodiment provides an aqueous inkjet ink that has excellent smear fastness, water fastness and high optical density (OD) while also providing excellent stability and jetting properties.

  Another embodiment provides an aqueous inkjet ink that includes certain thermal properties when the polyurethane is measured by dynamic mechanical analysis in an aqueous inkjet ink comprising SDP, polyurethane dispersion and water.

Accordingly, the aqueous inkjet ink composition comprises from about 1% to about 20% by weight of a self-dispersing pigment and from about 1% to about 10% by weight of polyurethane dispersion, wherein the polyurethane dispersion is from above −30 ° C. to 35%. Having a glass transition temperature Tg of less than
a. 1.7-5 × 10 ⁸ Pascal loss elastic modulus E ″,
b. The peak loss tangent is 0.23 to 0.65,
Wherein the glass transition temperature, peak loss tangent and loss modulus are measured by dynamic mechanical analysis on membranes prepared from polyurethane dispersions.

  Yet another embodiment provides an aqueous inkjet ink comprising a self-dispersing pigment dispersed in an aqueous medium, further comprising a polyurethane dispersion, wherein the polyurethane has the thermal properties described above. ing.

Self-dispersing pigments optionally contain an anionic hydrophilic chemical group, and optionally the chemical group contains a carboxyl group. These anionic hydrophilic groups are bonded to the surface with hypochlorous acid, sulfonic acid or ozone so that at least one functional group selected from the group consisting of carbonyl, carboxyl, hydroxyl and sulfone is bonded onto the surface of the pigment. It may be obtained by oxidative treatment. The oxidant may be ozone. Ozone is useful for producing self-dispersing carbon pigments from carbon black. The oxidized pigment may have an acid value of less than 3 μmol / M ² .

  Another embodiment provides a method of inkjet printing using the aqueous inkjet ink described above.

  Another embodiment provides an ink set that includes at least one other color ink-jet ink in addition to an aqueous ink-jet ink comprising SDP and a polyurethane having the thermal properties described above.

  One embodiment provides that the ink is particularly advantageous for printing on plain paper.

  Those skilled in the art will more readily understand these and other features and advantages of the present invention upon reading the following detailed description. Those skilled in the art may provide several features of the invention described above and below in connection with separate embodiments for clarity in combination in a single embodiment. I can recognize that. Conversely, various features of the invention described in connection with a single embodiment for brevity may be provided separately or in any subcombination. Further, singular references may also include the plural unless the context clearly indicates otherwise (eg, “a” and “an” may mean one or more). Further, reference to values stated as ranges include every and every value within that range.

  Unless defined or defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention is related.

  Unless otherwise specified, all percentages, parts, ratios, etc. are by weight. Where an amount, concentration or other value or parameter is shown as either a range, preferred range or a list of preferred upper and lower limits, this is independent of whether the range is disclosed separately. It should be understood that all ranges formed by any pair of any upper range limit or preferred value and any lower range limit or preferred value are specifically disclosed. When numerical ranges are listed herein, the ranges are intended to include all integers and fractions within the endpoints and ranges, unless otherwise specified.

  Where the term “about” is used in describing a value or endpoint of a range, the disclosure should be understood to include the specific value or endpoint referred to.

  As used herein, the term “dispersed” is composed of finely divided particles (often in the colloidal size range) in which one phase is distributed throughout the bulk material, which particles are either dispersed phase or It means a two-phase system that is an internal phase and whose bulk material is a continuous phase or an external phase. Bulk systems are often aqueous systems.

  The term “pigment” as used herein refers to any substance, usually in powder form, that imparts color to another substance or mixture. In addition, this definition includes disperse dyes, white and black pigments.

  As used herein, the term “HSD” means fast dispersibility.

  As used herein, references to enhanced or improved “print quality” include optical density, gloss and image discrimination (DOI) of printed images, as well as, for example, friction fastness (finger rub), water fastness (water droplets) ) And smear fastness (fluorescent pen stroke), etc., meaning that some aspects of fastness (resistance to ink removal from the printed image) are improved.

  As used herein, the term “OD” means optical density.

  As used herein, the term “SDP” means a “self-dispersible” or “self-dispersing” pigment.

  As used herein, the term “aqueous vehicle” means water or a mixture of water and at least one water-soluble organic solvent (co-solvent).

  As used herein, the term “substantially” means to a substantial extent almost all.

  As used herein, the term “Mn” refers to the number average molecular weight measured by size exclusion chromatography.

  As used herein, the term “Mw” means the weight average molecular weight measured by size exclusion chromatography.

  As used herein, the term “Pd” means polydispersity, which is the weight average molecular weight divided by the number average molecular weight.

  As used herein, the term “d50” means a particle size where 50% of the particles are smaller; “d95” means a particle size where 95% of the particles are smaller. .

  As used herein, the term “cP” means centipoise, a unit of viscosity.

  The term “prepolymer” as used herein means a polymer that is an intermediate in the polymerization process and can also be considered a polymer.

  As used herein, the term “AN” refers to acid number, ie, mg KOH per gram of solid polymer.

  As used herein, the term “neutralizing agent” is meant to encompass all types of agents that are useful for converting ionic groups to more hydrophilic ionic (salt) groups. means.

  The term “PUD” as used herein refers to the polyurethane dispersion described herein.

  As used herein, the term “DMIPA” means dimethylisopropylamine.

  As used herein, the term “DMPA” means dimethylolpropionic acid.

  As used herein, the term “TEA” means triethylamine.

  As used herein, the term “IPDI” means isophorone diisocyanate.

  As used herein, the term “NCO prepolymer” means a polymer having the characteristics of a polyurethane, but further reaction with isocyanates or isocyanate reactive groups to prepare higher molecular weight polymers.

Polyurethane dispersions having a glass transition temperature (Tg) above 30 ° C. and below 35 ° C. provide excellent smear resistance. Further having the glass transition temperature described above, and a. 1.7-5 × 10 ⁸ Pascal loss elastic modulus E ″,
b. The peak loss tangent is 0.23 to 0.65,
A polyurethane whose glass transition temperature Tg, peak loss tangent and loss modulus are measured by dynamic mechanical analysis on a film prepared from a polyurethane dispersion, having at least one of the following thermal properties: Has improved smear resistance.

  Smear resistance is measured by printing on plain paper and using a yellow highlighter across the printed image at various times after printing. The amount of smear is compared between the different polyurethanes tested. Those having the above-described Tg and loss elastic modulus and / or peak loss tangent were excellent in smear resistance. Another embodiment provides a polyurethane dispersion having both a loss modulus E "and a peak loss tangent within the above range.

In another embodiment, a polyurethane dispersion having a glass transition temperature Tg of greater than −30 ° C. to less than 35 ° C. with a loss modulus E ″ of 2.4-4.5 × 10 ⁸ Pascals may be used. In another embodiment, the polyurethane dispersion having a glass transition temperature Tg greater than −30 ° C. and less than 35 ° C. with a peak loss tangent may be 0.24 to 0.45. In yet another embodiment, the polyurethane dispersion has both a loss modulus E ″ of 2.4-4.5 × 10 ⁸ Pascal and a peak loss tangent of 0.24-0.45.

  It is known that some polyurethane dispersion additives improve the smear resistance of inkjet inks, especially for self-dispersing pigments. Polyurethane dispersions are likely to form a film when printed and protect the self-dispersing pigments that are most likely on the top surface of the substrate. Accordingly, there has been a demand for a film that is not constrained by theory but has a better adhesion to a substrate but does not have brittleness. Because of these properties, the dynamic mechanical thermal test described above was performed to find polyurethanes with higher glass transition temperatures Tg than those already described in US Pat. No. 7,176,248. I was supposed to. It has been found that films with excessively high Tg are highly brittle and “detach” from the SDP on the substrate and / or the substrate, with no result in improved smear resistance. However, the polyurethane having a Tg of -30 to 35 ° C does not fully describe the polyurethane, and the polyurethane also has other properties characterized by loss modulus and / or peak loss tangent. Had to be. While not being bound by theory, these thermal properties indicate that polyurethane films are sufficiently flexible to be able to deform under the stress of smear testing while retaining “association” with SDP particles on the surface of the substrate. It becomes possible to predict.

  The use of dynamic mechanical analysis is well known for characterizing polymers through their viscoelastic studies. The two parameters obtained from these tests are E ', which is the ratio of in-phase stress to applied strain, and E ", which is the ratio of out-of-phase stress to strain. E 'is related to the stored mechanical energy per cycle, and E "is related to the energy converted to heat through viscous dispersion. E ′ is called the storage elastic modulus, and E ″ is called the loss elastic modulus. The material loss factor or loss tangent is tan δ = E ″ / E ′, which represents the ratio of the dissipated energy to the energy stored per deformation cycle. In the physical sense, the storage modulus is related to the stiffness of the material and the loss modulus is reflected in the damping capacity of the material. At the peak tan δ value, the viscous force and the elastic force are balanced. The elastic force tends to compensate for the deformation of the printed image induced by the highlighter during the test. Loss tangent is the ratio of viscous force to elastic force. At the peak loss tangent value, the viscous force and the elastic force are balanced. The elastic force tends to compensate for image deformation induced by the highlighter during the test. If the loss tangent is significantly higher or lower than the peak value, the image becomes too brittle or soft and smears occur.

  A general discussion of dynamic mechanical analysis may be found in the Polymer Thermal Analysis section of the Encyclopedia of Polymer Science and Technology.

Polyurethane dispersion (PUD)
According to the present invention, the term “polyurethane dispersion” means an aqueous dispersion of a polymer containing urethane groups and optionally urea groups, as those skilled in the art understand this term. These polymers also incorporate hydrophilic functional groups to the extent required to maintain a stable dispersion of the polymer in water.

  The polyurethane is selected based on the evaluation of the thermal characteristics described above. In any given set of polyurethanes having a similar synthesis scheme, there may be only one that has the thermal properties described above for polyurethanes prepared in a seemingly similar manner. The preparation of the polyurethane will be described below.

  Polyurethane dispersions are polyurethane dispersions in which the polymer is preferentially stabilized in the dispersion through incorporated ionic functional groups, in particular anionic functional groups such as neutralized acidic groups. These polyurethanes are called anion-stabilized polyurethane dispersions. Further details are provided below.

  Such aqueous polyurethane dispersions first form an isocyanate-rich (N = C = O, NCO) prepolymer and then extend the chain in the aqueous phase, optionally in the presence of a multifunctional chain extender. It may be prepared by a step process. Polyurethanes with excess isocyanate reactive groups may also be used.

  Typically, in polyurethane formation, reacting a compound containing one or more isocyanate reactive groups as well as at least one compound with an isocyanate group or isocyanate reactive group containing one acidic group or acidic base with a diisocyanate, An intermediate product is formed. The molar ratio of isocyanate groups to isocyanate reactive groups may vary from 1.0: 1.5 to 1.0: 0.67.

Diisocyanates suitable for reacting with isocyanate-reactive compounds containing ionic groups (or groups that may be imparted with ionicity, for example through neutralization) are aromatic, cycloaliphatic or aliphatically bonded isocyanate groups Any of these are included. More suitable diisocyanates include any diisocyanate useful for preparing polyurethanes and / or polyurethane-ureas from polyether glycols, diisocyanates and diols, or amines may be used. Suitable polyisocyanates are those containing either aromatic, alicyclic or aliphatic groups attached to isocyanate groups. Mixtures of these compounds may be used. Suitable compounds are those with an isocyanate bonded to an alicyclic or aliphatic moiety. Where aromatic isocyanates are used, it is appropriate that alicyclic or aliphatic isocyanates are present as well. R ₁ may be substituted with an aliphatic group.

Examples of suitable diisocyanates include 2,4-toluene diisocyanate (TDI); 2,6-toluene diisocyanate; trimethylhexamethylene diisocyanate (TMDI); 4,4′-diphenylmethane diisocyanate (MDI); 4,4′-dicyclohexyl. Methane diisocyanate (H ₁₂ MDI); 3,3′-dimethyl-4,4′-diphenyl diisocyanate (TODI); dodecane diisocyanate (C ₁₂ DI); m-tetramethylene xylylene diisocyanate (TMXDI); 1,4-benzene Diisocyanate; trans-cyclohexane-1,4-diisocyanate; 1,5-naphthalene diisocyanate (NDI); 1,6-hexamethylene diisocyanate (HDI); 4,6-xylylene diisocyanate Over preparative; isophorone diisocyanate (IPDI); and although combinations thereof, but is not limited thereto. IPDI and TMXDI are most appropriate.

  Small amounts of less than about 3% by weight monoisocyanate or polyisocyanate, based on the weight of the diisocyanate, may be used in the mixture with the diisocyanate. Examples of useful monoisocyanates include alkyl isocyanates such as octadecyl isocyanate and aryl isocyanates such as phenyl isocyanate. Examples of polyisocyanates are triisocyanatotoluene HDI trimer (Desmodur 3300), and polymeric MDI (Mondur MR and MRS).

  Isocyanate-reactive compounds containing acidic groups, ie carboxylic acid groups, carboxylate groups, sulfonic acid groups, sulfonate groups, phosphonic acid groups and phosphonate groups, are chemically incorporated into the polyurethane to provide hydrophilicity and In a stable manner in an aqueous medium. Acidic salts are formed by neutralizing the corresponding acidic groups either before, during or after formation of the NCO prepolymer, and suitably after formation of the NCO prepolymer. Isocyanate-reactive compounds containing sulfonic acid groups may be used.

  Examples of sulfonic acids include diols with sulfonic acid substituents. An example is N-bis (2-hydroxyethyl) -2-aminoethane-sulfonic acid.

  Suitable compounds for incorporating carboxyl groups are described in US Pat. No. 3,479,310, US Pat. No. 4,108,814 and US Pat. No. 4,408,008. A neutralizing agent for converting a carboxylic acid group to a carboxylate base is described below.

Carboxy group-containing compounds include hydroxyl-carboxylic acids corresponding to the formula (HO) _x Q (COOH) _y , where Q is a linear or branched hydrocarbon radical containing 1 to 12 carbon atoms. X is 1 or 2, suitably 2; y is 1 to 3, more suitably 1 or 2, and most suitably 1.

  Examples of these hydroxy-carboxylic acids include citric acid, tartaric acid and hydroxypivalic acid.

  Particularly suitable acids are those of the above structural formula where x = 2 and y = 1. These dihydroxyalkanoic acids are described in US Pat. No. 3,420,054. Particularly suitable dihydroxyalkanoic acids are

An alpha, alpha-dimethylolalkanoic acid represented by Structural Formula I, wherein Q 'is hydrogen or an alkyl group containing from 1 to 8 carbon atoms. The most suitable compound is alpha, alpha-dimethylolpropionic acid (DMPA), where Q 'in structural formula I above is methyl.

  The acidic groups are incorporated in an amount sufficient to provide an ionic group content of at least about 10, more suitably at least about 18 milligrams of KOH per gram of polyurethane resin solids. The upper limit of acidic group content is about 100, more preferably about 70 and most preferably about 60 milligrams per gram of polyurethane resin solids.

  A suitable higher molecular weight isocyanate reactive group may be a polyol containing at least two hydroxyl groups. These may be reacted with preadducts to prepare NCO prepolymers having a molecular weight of about 400 to about 6000, suitably about 800 to about 3000 and more suitably about 1000 to about 2500. The molecular weight is the number average molecular weight (Mn) and is determined by end group analysis (OH number, hydroxyl analysis). These high molecular weight compounds include polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyester amides and polyhydroxy polythioethers. A combination of polyols may be used in the polyurethane. Polyester polyols, polyether polyols and polyhydroxy polycarbonates are most suitable.

  Poly (meth) acrylates containing hydroxyl groups include those common in addition polymerization techniques such as cation, anion and radical polymerization. Most suitable is alpha-omega diol. An example of these types of diols are those prepared by “living” or “controlled” or chain transfer polymerization processes that allow the placement of one hydroquinle at or near the end of the polymer.

  In special cases where slight branching of the NCO prepolymer or polyurethane is desired, in addition to the above components that are suitably difunctional in the isocyanate polyaddition reaction, trimethylolpropane or 4-isocyanantmethyl-1 , 8-octamethylene diisocyanate and other multifunctional components generally known in polyurethane chemistry and a few trifunctional or higher functional components may be used. However, the NCO prepolymer must be substantially linear, and this may be achieved by maintaining the average functionality of the prepolymer starting component at 2: 1 or less.

  Other optional compounds include isocyanate-reactive compounds containing lateral or terminal hydrophilic ethylene oxide or propylene units. Isocyanate-reactive compounds for incorporating lateral or terminal hydrophilic ethylene oxide units may contain one or two isocyanate reactive groups, suitably hydroxy groups. Other optional compounds include isocyanate-reactive compounds that contain self-condensable moieties. The content of these compounds depends on the desired level of self-condensation necessary to provide the desired resin properties. 3-Amino-1-triethoxysilyl-propane is an example of a compound that reacts with an isocyanate through an amino group and self-condenses through a silyl group when reversed to water.

  NCO rich polyurethanes are typically prepared by chain extending an NCO prepolymer. Suitable chain extenders are polyamine chain extenders that may optionally be partially or fully blocked. Preparation of an aqueous polyurethane dispersion by mixing at least partially blocked diamine or hydrazine chain extender and NCO prepolymer in the absence of water and then adding the mixture to water. Upon contact with water, the blocking agent is released and the resulting unblocked polyamine reacts with the NCO prepolymer to form a polyurethane.

  Optionally, the polyurethane dispersed polyurethane is based on a chain-extended isocyanate-functional polyurethane prepolymer, wherein the isocyanate-functional polyurethane prepolymer has an isocyanate functional group equivalent weight of the isocyanate-reactive functional group. A prepolymer prepared by reacting a diisocyanate with at least one isocyanate reactive group with an acidic group or acidic base greater than an equivalent and at least one compound comprising one or more isocyanate reactive groups.

  Suitable blocked amines and hydrazines include reaction products of polyamines with ketones and aldehydes to form ketimines and aldimines, and hydrazines and ketones to form ketazines and aldazines, ketone hydrazones and aldehyde hydrazones. Reaction with aldehyde is included. The at least partially blocked polyamine has at least one primary or secondary amino group and at least one blocked primary that releases a free primary or secondary amino group in the presence of water. Contains a secondary or secondary amino group.

  Suitable polyamines for preparing at least partially blocked polyamines have an average functionality of 2 to 6, suitably 2 to 4 and more suitably 2 to 3 or the number of amine nitrogens per molecule . The desired functional group may be obtained by using a mixture of polyamines containing primary or secondary amino groups. The polyamine is generally an aromatic, aliphatic or cycloaliphatic amine and contains 1 to 30, suitably 2 to 15 and more suitably 2 to 10 carbon atoms. These polyamines may contain additional substituents provided that they are not as reactive with isocyanate groups as primary or secondary amines. These same polyamines may be partially or fully blocked polyamines.

  Suitable polyamines include 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine or IPDA), bis- (4-amino-cyclohexyl) -methane, bis- (4-amino-3 -Methylcyclohexyl) -methane, 1,6-diaminohexane, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. Hydrazine is suitable as well.

  The amount of chain extender when the polyurethane is rich in NCO depends on the number of terminal isocyanate groups in the prepolymer. The ratio of prepolymer terminal isocyanate groups to chain extender isocyanate reactive groups is between about 1.0: 0.6 to about 1.0: 1.1 on an equivalent basis, more suitably about 1.0: It is between 0.8 and about 1.0: 0.98. Any isocyanate group that is not chain extended with an amine reacts with water that functions as a diamine chain extender.

  Chain extension may occur prior to the addition of water in the process, but typically occurs by combining the NCO prepolymer, chain extender, water and any other components with agitation. .

  Other monomers and / or oligomers that do not chemically participate in the polyurethane synthesis may be added. Additions may be made at any point during the synthesis cycle as long as they do not interfere with the polyurethane synthesis at all. A specific example of a compatible oligomer / monomer is styrene allyl alcohol, abbreviated SAA.

  Molecular weight is also a property of polyurethane that may be used to define polyurethane. Molecular weight is usually reported as weight average molecular weight Mw. A suitable molecular weight is greater than 14,000 as Mw. The polyurethane binder is not limited to a molecular weight Gaussian distribution and may have other distributions such as a bimodal distribution.

  The particle size of the polyurethane dispersion is typically in the range of about 30 to about 100,000 nm. A suitable range of polyurethane binder for inkjet inks is from about 30 to about 350 nm.

  In order to obtain a stable dispersion, a sufficient amount of acidity so that when combined with any hydrophilic ethylene oxide unit, the resulting polyurethane remains stably dispersed in the aqueous medium. The group must be neutralized. Generally, at least about 75%, more suitably at least about 90% of the acid groups are neutralized to the corresponding carboxylate base.

  Suitable neutralizing agents for converting acidic groups to bases either before, during or after incorporation into the NCO prepolymer include tertiary amines, alkali metal cations and ammonia. Suitable trialkyl substituted tertiary amines such as trimethylamine, tripropylamine, dimethylcyclohexylamine and dimethylethylamine may be used.

  Neutralization may occur at any point in the process. A typical procedure involves neutralization of at least a portion of the prepolymer, which is then chain extended in water in the presence of additional neutralizing agent.

  The final product is a stable aqueous dispersion of polyurethane particles having a solids content of up to about 60% by weight, suitably about 15 to about 60% by weight and more suitably about 30 to about 45% by weight. However, it is always possible to dilute the dispersion to any desired minimum solids content. In any suitable order of addition, stable aqueous dispersions of polyurethane particles, ink vehicles, self-dispersing pigments and other ink components are combined.

Self-dispersing pigment (SDP)
As pointed out previously, SDP is in a general sense and well known to those skilled in the art.

  Typically, SDP is a pigment that has been surface treated to provide self-dispersibility in water such that a separate dispersant is not required. The pigment may be black, such as carbon black, or may be a colored pigment such as PB 15: 3 and 15: 4 cyan, PR 122 and 123 magenta and PY 128 and 74 yellow.

  The surface of the pigment may be treated so that at least one functional group selected from the group consisting of carbonyl, carboxyl, hydroxyl and sulfone groups or salts thereof is bonded on the surface. This surface treated pigment can be obtained by grafting functional groups or molecules containing functional groups onto the surface of the pigment, or by physical treatment (eg vacuum plasma) or chemical treatment (eg hypochlorous acid, sulfonic acid). Etc.). One or more types of functional groups may be grafted onto the pigment particles. The type and degree of grafting of one or more functional groups may be appropriately determined by taking into account such things as dispersion stability in the ink, color density, and drying characteristics at the front end of the inkjet head. .

Black pigments that can be used in the present invention may be produced, for example, by the method described in US Pat. No. 6,852,156. The carbon black treated by the method described in this publication has a surface active hydrogen content that is neutralized with a base to provide a very stable dispersion in water. It is also possible to apply this method to colored pigments. A suitable oxidizing agent, especially for carbon black, is ozone. Suitable oxidized pigments have an acid number of less than 3 μmol / M ² .

  Commercially available SDP products may be used. Examples include Microjet CW1 manufactured by Orient Chemical Industries, Ltd. and Cab-O-Jet 200 and 300 manufactured by Cabot Corporation.

  As suitable for inkjet, a variety of organic and inorganic pigments are known in the art, either alone or in combination. As with any pigmented ink jet ink, care must be taken to ensure that the pigment particles are small enough to avoid clogging or clogging the nozzle orifice used to fire the ink. Small pigment particles also affect the stability of the pigment dispersion, which is crucial throughout the life of the ink.

  Useful particle sizes are typically in the range of about 0.005 microns to about 15 microns. The pigment particle size should be in the range of about 0.005 to about 5 microns, more suitably about 0.005 to about 1 micron and most suitably about 0.005 to about 0.3 microns.

Percentage of Main Component The pigment level used in this ink is the level typically required to impart the desired color density to the printed image. Typically, the pigment level is from about 0.01% to about 20% by weight of the ink.

  The polyurethane dispersion is selected based on the thermal parameters described above, and the amount used in the ink is affected by the required degree of fixing and the range of acceptable ink properties. Typically, the polyurethane dispersion level will be in the range of up to about 10%, suitably about 0.1% to about 10%, more suitably about 0.2 to about 4% by weight of the ink. . In many cases, even a very low polyurethane dispersion level may result in some degree of improved ink fusing. Higher levels provide better fixing, but generally at some point the viscosity increases excessively and jetting performance is unacceptable. The correct balance of properties must be determined for each situation, and this determination may generally be made by routine experimentation well within the skill of the artisan.

A combination of two or more polyurethane dispersions may also be utilized. The polyurethane dispersion may be used in combination with other binders such as polyacrylate / polymethacrylate.
Other Components The inkjet ink may contain other components that are well known in the art. For example, anionic, nonionic, cationic or amphoteric surfactants may be used. In aqueous inks, the surfactant is typically present in an amount of about 0.01 to about 5%, suitably about 0.2 to about 2%, based on the total weight of the ink.

  A co-solvent may be included to improve the blockage inhibiting properties of the ink composition. This “pluggage” feature is manifested by observing blocked nozzles that result in a degradation of the printed image.

  Biocides may be used to prevent microbial growth.

  In order to eliminate the harmful effects of heavy metal impurities, sequestering agents such as EDTA may also be included.

  Other known additives may also be added to improve various properties of the ink composition as desired. For example, penetrants such as glycol ethers and 1,2-alkanediols may be added to the formulation.

  For glycol ether, ethylene glycol monobutyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether Diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, Propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dip Propylene glycol mono -n- butyl ether, dipropylene glycol mono -n- propyl ether and dipropylene glycol mono - iso - include propyl ether.

A suitable 1,2-alkanediol is 1,2-C _1-6 alkanediol, more suitably 1,2-hexanediol.

  The amount of one or more glycol ethers and one or more alkanediols added should be appropriately determined, but is typically about 1 to about 5 weights based on the total weight of the ink % And more typically from about 2 to about 10% by weight.

Thermal Properties of Polyurethane Dispersions The thermal properties of polyurethanes were tested by preparing polyurethane films. The concentrated polymer solution (about 40%) was diluted with water until the total solids was 18%. In addition, up to 1% butyl cellosolve was added to the sample. The sample was placed in a vial and the vial itself was evacuated in a vacuum chamber for 3 hours. The bubble free polymer solution was gently poured into a 50 mm PTFE dish and dried in an oven at 70 ° C. overnight. Then, the sample was taken out from the dish, reversed and placed on the PE film, and the bottom side was further dried. It was important to ensure that there were no bubbles in the membrane.

  The membrane was cut into a rectangle of about 3 cm × 1 cm and sandwiched on the sample holder of SEIKO DMS210 Tensile Mode Analyzer. The temperature in the chamber was varied from −150 C to 100 C while the sample was deformed in the linear viscoelastic region. The deformation amplitude was less than 10 microns and the frequency was 1 Hz. From the tension data, storage (elastic) and loss (viscous) moduli were determined and plotted automatically. The glass transition temperature was determined from the peak of the loss modulus curve.

  Test equipment used: DMS210 (for tensile construction) with SDM5600 controller from Seiko Instruments Inc. Analyzer: Temperature range; -150-500C; RT Instruments; Available from Woodland, CA.

Ink characteristics The ejection speed, drop separation length, drop size and flow stability are greatly affected by the surface tension and viscosity of the ink. Pigment inkjet inks suitable for use with inkjet printing systems are from about 20 mN / m (dyne / cm) to about 70 mN / m (dyne / cm) at 25 ° C., more suitably from about 25 to about 40 mN / m ( It must have a surface tension in the range of dynes / cm). The viscosity is in the range of about 1 mPa · s (cP) to about 30 mPa · s (cP) at 25 ° C., more suitably in the range of about 2 to about 20 mPa · s (cP). The ink has physical properties compatible with a wide range of ejection conditions, such as pen drive frequency and nozzle shape and size. The ink must have excellent storage stability over a long period of time. Furthermore, the ink must not corrode the parts of the inkjet printing device that come into contact with it, and must be essentially odorless and nontoxic. Suitable inkjet printheads include (but are not limited to) those with piezoelectric and thermal droplet generators.

Evaluation of Inkjet Inks with Polyurethane Dispersion Aqueous inkjet ink with polyurethane dispersion is prepared by adding polyurethane dispersion, self-dispersing pigment, water, and other ink ingredients listed above in any suitable order. It was.

  The ink tested used a black SDP prepared, for example, according to any one of Examples 1-7 according to the invention in US Pat. No. 6,852,156.

  Evaluate the ink by printing on plain paper such as Hammermill Copy Plus and Xerox 4024 using an inkjet printer such as Epson Stylus Color 980 set for high speed, 720 dpi; no color adjustment; highest definition; Good.

  Optical density and color (LabCh) measurements are made using a Greytag spectro-densiometer set to “Status 1” (narrowband) and “absolute” for optical density measurements.

  The print quality is determined by printing a test pattern and observing the test pattern printed in this way. The squares that make up the pattern (10 mm × 10 mm) are printed at 720 dpi on either Hammermill Copy Plus or Xerox 4200 paper. Inspect the printed squares for “white lines” using a magnifying glass. Typically, the presence of a white line indicates nozzle clogging and / or misalignment. Samples are rated as follows. “P” (not possible) or 0 to 1: many “white lines” are present; “F” (possible) or 2-3: few “white lines” are present; “G” or 4 to 5: “white” There is no line. A failure rating is almost the same as a failure, and an OK rating is equivalent to good. If the printer used does not have a setting of 720 dpi, the “high quality” setting is used.

  For inks without binders, water fastness tends to be somewhat variable between different plain paper brands. The polyurethane binders of the present invention compensate for any lack of waterfastness, and thus the inks of the present invention provide excellent waterfastness on a daily basis regardless of the paper used.

  The inks of the present invention have beneficial image properties such as high OD, water resistance and smear resistance in relatively low viscosity formulations, eg, less than about 5 mPa · s (Brookfield viscometer with LVT adapter at 20 ° C.). However, no particular limitation on viscosity is shown.

  To determine smear, the print was tested and assigned a 1, 2, 3 or 4 smear score. A pattern consisting of 5 parallel stripes with a width of 4 mm spaced about 7 mm apart was printed on the printer using a setting of 720 dpi. One and two overlapping strokes were drawn with fluorescent markers across the five printed lines. For example, Hi-Liter (registered trademark) manufactured by Avery Dennison Corp, Zebra (registered trademark) manufactured by Zebra Co., Ltd., a pilot manufactured by Pilot Corporation, a fluorescent marker manufactured by Sanford Company, and an ecological product manufactured by Mitsubishi Pencil Co., Ltd. Appropriate highlighters such as lighters are available. The fluorescent markers used in the test are from Avery Dennison and Sanford. These pens are both alkaline and acidic and have variable friability. This process was performed on different parts of the test pattern at various time intervals, such as 1 minute, 10 minutes and 1 hour after printing the test pattern. Stripes were examined and rated for smear fastness. The scores from each stripe were added and the average was calculated. This process was repeated for three different printed pages. P ″ (not possible) or 1—strong evidence of significant smear including distortion of printed image; “F” (possible) or 2, substantial evidence of smear, but little distortion of printed image, fluorescent marker G (good) or 3, in which case some smearing of the ink was observed and almost no ink transferred to the fluorescent marker; and E (excellent) or 4, in this case No smearing of the ink was observed, and no ink was transferred to the fluorescent marker.

  The molecular weight of the polyurethane dispersion is measured by size exclusion chromatography. A solution of the polymer in tetrahydrofuran (THF) is injected into a series of columns containing a packing of porous material of constant pore size. Solute and solvent molecules diffuse through the pores, where the polymer is fractionated based on molecular size. The resulting data is then compared to known molecular weight polystyrene standards and calculated using the elution volume information.

  The particle size for both pigment and polyurethane dispersion is determined by dynamic light scattering. For the examples, a Microtrac UPA 150 analyzer from Honeywell was used. This technique is based on the relationship between particle velocity distribution and particle size. Light generated by the laser from each particle is scattered and is Doppler shifted by the Brownian motion of the particle. The frequency difference between the shifted and unshifted light is amplified, digitized and analyzed to recover the particle size distribution.

  The inks of the present invention generally exhibit storage stability. Thus, the ink may withstand high temperatures in closed containers for extended periods of time (eg, 70 ° C. for 7 days) without a substantial increase in viscosity or particle size.

  The advantages of the present invention are realized without any special post-processing after printing. Although no “fixing” step, such as heat or UV curing or treatment with a reaction solution, is required, such work may be useful for other reasons and no particular limitations are implied.

  In these examples, the following components were utilized.

  Other common chemicals were obtained from Aldrich or equivalent chemical sources.

  Polyurethane is generally produced by a known synthesis method. In general, the polyurethane components are added together in any suitable order. The chemical constituents are isocyanate-reactive compounds, isocyanate compounds and isocyanate-reactive or isocyanate compounds with ionic substituents that stabilize the polyurethane dispersion. An organic solvent is often used for the initial reaction, followed by addition of water to obtain a dispersion. Neutralize ionic substituents prior to or at the time of addition of water.

Synthesis of polyurethane dispersions Table 1 lists various synthesis parameters for the polyurethanes tested. The synthesis parameters listed in Table 1 are as follows:
1. The diol is an isocyanate reactive group and is:
a. PCD polycarbonate diol b. PCD / polyester diol (mixture of polycarbonate diol and polyester diol)
c. Polyester diol d. 1. Polyether diol Diol MW
3. Active polyurethane component diol wt%
4). Isocyanate wt% of active polyurethane component. Except where noted, isophorone diisocyanate was used.
5. The type of acid in the compound with an ionic substituent: “C” corresponds to the carboxylic acid type, and specifically dimethylolpropionic acid, “S” is the sulfonic acid and specifically N, N-bis. Corresponds to (2-hydroxyethyl) -2-aminoethane-sulfonic acid.
6). Neutralizing agent7. % Of ionic groups neutralized by neutralization
8). The process modification points out whether the ionic group compound is added before or after other diols. PMP corresponds to a prepolymer mixing process in which the solvent, diol, isocyanate, and acid-containing components are all added together. Acid 1 ^st means that the acid-containing component is added to the solvent, followed by the isocyanate, followed by the diol. acid 2 ^nd is a diol and isocyanate reactants were added to the solvent; it reacted to diol reacts all; and corresponds to the addition of subsequent acid component.
9. Reaction solvent: acetone (referred to herein as Ace), N-methylpyrrolidinone (referred to herein as NMP)
10. _{Mn of} PUD and _{Mw of} final polyurethane as measured by size exclusion chromatography.

Polyurethane dispersion 17; Preparation Example 177.5 g NMP, 56.2 g N, N for an alkali and acid free dry flask equipped with an addition funnel, condenser, mechanical stirrer and nitrogen gas line -Bis (2-hydroxyethyl) -2-aminoethane-sulfonic acid was added. The contents were heated to 60 ° C. and mixed well. To the flask, 0.62 g of DBTL was added as a shot and the flask was charged with 171.1 g of IPDI through an addition funnel over 15 minutes. All residual IPDI was washed out of the addition funnel with 20.4 g NMP and poured into the flask.

  The flask temperature was raised to 65 ° C. and then held for 415 minutes until all solid material had reacted and dissolved. To control the exotherm, 366.2 g of polyester diol (adipic acid / 1,6 hexanediol / isophthalic acid) was added to the reaction flask in 70-80 g increments. The reaction mixture was reacted at 65 ° C. for 75 minutes until the NCO content was less than 1.64% (wt%). The mixture was cooled to 35 ° C. and 59.5 grams of NMP was added to reduce the viscosity.

  528 g of 2% NaOH solution at a temperature of 35 ° C. for 3 minutes, then 560.1 g of deionized water for 10 minutes, then 6.25% ethylenediamine in water for 5 minutes (referred to herein as EDA) ) Was added via a separate addition funnel, which was then flushed with 200.0 g of water. The mixture was stirred for 1 hour at room temperature and then held at 45 ° C. for 2 hours.

The final polyurethane dispersion has a solids content of 26.4% (% by weight), an average particle size (d ₅₀ ) of 18 nm and a Brookfield viscosity (5 rpm) of 60 cPs.

Example of Preparation of Comparative Polyurethane Dispersion 2 385 g of Desmophene C1200 (polyester carbonate diol commercially available from Bayer) for an alkali and acid free dry flask equipped with an addition funnel, condenser, stirrer and nitrogen gas line ), 3.0 g Zonyl® TL (a fluorosurfactant commercially available from DuPont), and 120 g acetone and 0.04 g DBTL. The contents were heated to 40 ° C. and mixed well. 122.7 g of IPDI was then added to the flask via the addition funnel at 40 ° C. for 60 minutes, and any residual IPDI was flushed from the addition funnel into the flask using 15.5 g of acetone.

  The flask temperature was raised to 50 ° C. and then held for 30 minutes. 32.3 g of DMPA followed by 21.9 g of TEA was added to the flask via the addition funnel, which was then flushed with 15.5 g of acetone. The flask temperature was then raised again to 50 ° C. and held at 50 ° C. until the NCO% was below 1.45%.

  At a temperature of 50 ° C., 705 g of deionized (DI) water was added over 10 minutes and then 71 g of EDA (as a 6.25% solution in water) over 5 minutes via the addition funnel. Then it was washed off with 20.0 g of water. The mixture was held at 50 ° C. for 1 hour and then cooled to room temperature.

  Acetone (-150.0 g) was removed under vacuum, leaving a final polyurethane dispersion with about 35.0 wt% solids and an average particle size of 37 nm.

  Examples 1 to 21 according to the invention; polyurethane dispersion

Diol used:
PUD1, Eternacol UH-50; 1,6-hexanediol based polycarbonate diol from UBE Chemical PUD2, 11, 13 and 14, Desmophene; hexanediol based carbonate co-caprolactone diol PUD3, Stepanpol PD56 commercially available from Bayer Orthophthalate-diethylene glycol based aromatic polyesters PUD4, 16, 17, 18 and 19, commercially available from Stepan, adipic acid / 1,6 hexanediol / isophthalic acid PUD5, 7, 9 and 10, polytetramethylene glycol; TERATHANE650
PUD 6 and 8; Stepan PD200LV; orthophthalate-diethylene glycol-based aromatic polyester PUD12, polytetramethylene glycol, TERATHANE 1000, commercially available from Stepan
Polycarbonate diol based on PUD 19 and 20,1,6-hexanediol; Eternacol UH-200 commercially available from UBE Chemical
Measured acid number for selected polyurethane PUD5, 90
PUD6, 30.6
PUD17, 25
PUD19, 30.6
PUD9 and PUD10 are synthetic replicas.
PUD20 and PUD21 are synthetic replicas.

  Comparative Examples 1-9; polyurethane dispersion

  Composition V: Comparative PUD 1 is Mace 85-302, a polyurethane dispersion commercially available from Mace Adhesives and Coatings, Dudley Massachusetts.

Diol used Comparative PUDs 2, 3, 5, 7 and 8, Desmophene, a carbonate cocaprolactone diol based on hexanediol commercially available from Bayer
PUD4 for comparison, polytetramethylene glycol, TERATHANE1400
Comparative PUD5, Priplast 3192; dimer acid (C36) based polyester diol commercially available from Unichema

Ink Preparation and Testing All inks were prepared using black SDP. In order to the slurry of black SDP in deionized water, polyurethane dispersion binder, glycerol, ethylene glycol and Surfynol 465 surfactant were added in order. After mixing for 10-20 minutes, the pH was adjusted to a final value of 8 with triethanolamine. The ink was then filtered through a 5 micron filter and degassed.

  The ink was evaluated by printing on plain paper using an Epson stylus color 980 set to 720 dpi; no color adjustment; highest definition; high speed. A smear test was performed on these samples. The optical density was compared with the results for the printed material from the comparative PUD1, and the notation “+” means that the OD of the printed material was superior to the comparative example, and “=” was equal to the OD of the comparative example. "-" Means that the OD is lower than that of the comparative example.

  Table 4 shows the results for Examples 1-21 according to the present invention. The table shows the results of smear rating, optical density and three thermal parameter tests for polyurethane dispersion.

  Polyurethane dispersions that meet both the loss modulus and peak loss tangent criteria for selecting polyurethane when tested for thermal parameters are 4, 6, 8, 11, 17, 20, and 21.

  Comparative polyurethanes were formulated into ink forms and tested in a manner similar to inks according to the present invention. The results are reported in Table 5.

  The comparative polyurethane dispersion resulted in lower smear performance than the polyurethane dispersion according to the invention.

Claims (19)

An aqueous inkjet ink composition comprising from about 1 wt% to about 20 wt% self-dispersing pigment and from about 1 wt% to about 10 wt% polyurethane dispersion, wherein the polyurethane dispersion is greater than -30C to 35C Having a glass transition temperature Tg of less than
a. 1.7-5 × 10 ⁸ Pascal loss elastic modulus E ″,
b. The peak loss tangent is 0.23 to 0.65,
Wherein the glass transition temperature Tg, the peak loss tangent and the loss modulus are measured by dynamic mechanical analysis on a film prepared from a polyurethane dispersion. A water-based inkjet ink composition. The polyurethane dispersion has a loss modulus E ″ of 1.7 to 5 × 10 ⁸ Pascal, and the peak loss tangent is 0.23 to 0.65, where the peak loss tangent and the loss elasticity are The aqueous inkjet ink composition of claim 1, wherein the rate is measured by dynamic mechanical analysis on a film prepared from the polyurethane dispersion. The polyurethane dispersion has a loss modulus E ″ of 2.4 to 4.5 × 10 ⁸ Pascals, where the loss modulus is a dynamic machine for membranes prepared from the polyurethane dispersion The aqueous inkjet ink composition of claim 1, which is measured by analysis.   The polyurethane dispersion has a peak loss tangent of 0.24 to 0.45, wherein the peak loss tangent is measured by dynamic mechanical analysis on a membrane prepared from the polyurethane dispersion. 2. The aqueous inkjet ink composition according to 1.   The water-based inkjet ink composition according to claim 1, wherein the self-dispersing pigment is a self-dispersing carbon black pigment containing an anionic hydrophilic chemical group.   The ink according to claim 5, wherein the anionic hydrophilic chemical group on the self-dispersing carbon black pigment contains a carboxyl group.   The self-dispersing pigment is oxidized on the surface with hypochlorous acid, sulfonic acid or ozone so that at least one functional group selected from the group consisting of carbonyl, carboxyl, hydroxyl and sulfone is bonded onto the surface of the pigment. The water-based inkjet ink composition of claim 1, comprising a chemically treated pigment.   The water-based inkjet ink according to claim 1, wherein the self-dispersing pigment includes a pigment whose surface is oxidatively treated with ozone.   The water-based inkjet ink according to claim 1, wherein the polyurethane dispersion is an anion-stabilized polyurethane dispersion.   The aqueous inkjet ink of claim 1, wherein the polyurethane of the polyurethane dispersion has an acid number measured for the polyurethane in the polyurethane dispersion of 10 to 100 mg KOH / gram.   The aqueous inkjet ink of claim 1, wherein the polyurethane of the polyurethane dispersion has a weight average molecular weight greater than about 14,000.   The aqueous inkjet ink composition of claim 1, wherein the polyurethane of the polyurethane dispersion is substituted with a sulfonate ion group.   The aqueous inkjet ink of claim 1, wherein a combination of two or more polyurethane dispersions is used.   The ink of claim 1, wherein the ink has a surface tension in the range of about 20 mN / m to about 70 mN / m at 25 ° C. and a viscosity in the range of about 1 mPa · s to about 30 mPa · s at 25 ° C. Water-based inkjet ink. In an inkjet printing method comprising ejecting ink onto a substrate, the ink comprises from about 1% to about 20% by weight of a self-dispersing pigment and from about 1% to about 10% by weight of a polyurethane dispersion. An aqueous inkjet ink, wherein the polyurethane dispersion has a glass transition temperature Tg of greater than −30 ° C. to less than 35 ° C .;
a. 1.7-5 × 10 ⁸ Pascal loss elastic modulus E ″,
b. The peak loss tangent is 0.23 to 0.65,
Wherein the glass transition temperature Tg, the peak loss tangent and the loss modulus are measured by dynamic mechanical analysis on a film prepared from a polyurethane dispersion. ,Method.   The method of claim 15, wherein the substrate is plain paper.   The method of claim 15, wherein the self-dispersing pigment is self-dispersing carbon black.   The method of claim 15, wherein the polyurethane dispersion is an anion-stabilized polyurethane dispersion.   The method of claim 15, wherein the ink comprises about 0.01 to about 10 wt% pigment and 0.1 to about 10 wt% polyurethane based on the weight of the ink.